In this, Erythrosuchids constitute an Archosauriformes clade that is an outgroup to the Archosauria proper.

依照这个方法，引鳄科个初龙形动物演化，是初龙的外群。

What does group membership mean? How should we measure it? Ingroup vs. outgroup.

群的意思是什麽？我们应如何衡量？圈内与圈外。